The broad, long-term objective of this project is to discover acquired genetic alterations in human malignant mesothelioma. The proposed investigations emphasize three prominent sites of chromosomal deletion (9p21-p22, 1p21-p22, and 6q15-q2l) documented in malignant mesothelioma, each of which is also a frequent site of allelic loss in a variety of more common malignancies such as breast cancer. This project proposes to analyze the role of the putative tumor suppressor gene p16/MTS1/CDK4- inhibitor, located in 9p21-p22, in malignant mesothelioma and determine whether other genes from this chromosomal region are also altered in these tumors. Mesothelioma cell lines displaying homozygous deletions of 9p21-p22 that do not overlap the p16 locus will be examined to determine if another candidate tumor suppressor gene(s) is involved in these cases. An emphasis will be placed on studies of primary tumor tissues to determine whether p16 or a neighboring locus is the critically altered 9p21-p22 gene in malignant mesothelioma. This project also proposes to positionally clone and characterize the putative tumor suppressor gene located in 1p21-p22. Other fine deletion mapping studies will define molecularly the critically deleted segment in 6q15-q21, in preparation for the eventual cloning of the putative tumor suppressor gene(s) located in this region. In addition, differential messenger RNA display and a combination of comparative genomic hybridization and loss of heterozygosity analyses will be employed to identify other recurrent genetic changes contributing to the pathogenesis of malignant mesothelioma.